1. Field of the Invention:
The present invention relates to a method of extracting liposoluble components contained in microbial cells, and more particularly to a method of extracting and recovering, in a highly efficient and safe manner, liposoluble components contained in microbial cells.
2. Description of the Related Art:
Microorganisms such as filamentous fungi, yeast, and algae have ability to produce lipids. Therefore, there have been practiced a variety of methods to extract lipids from microbial cells endowed with lipid-producing ability.
Lipid is generally accumulated in microbial cells, and there are known such methods that extract lipid directly from microbial cells or by descructing cell walls mechanically or by means of enzymes.
There has been known a method of extracting a liposoluble material in the following way: microbial cells having the ability to produce oils and fats are suspended in ethanol and then destructed, and the suspension is subsequently subjected to filtration and centrifugation so as to separate ethanol. An extraction solvent is added to suspend the contents, which are then subjected to destruction for extraction (as described in, e.g., Japanese Patent Application Laid-Open (kokai) Nos. 61-170397, 61-227790, 62-44170, and 62-179598).
Of these methods, the invention disclosed in Japanese Patent Application Laid-Open (kokai) No. 61-170397 relates to a multistep extraction method, in which each step requires use of a different kind of solvent such as an alcoholic solvent or a hydrocarbon solvent. Moreover, each step must involve means for separating an organic solvent from the cells. Therefore, the method has the drawback of intricate procedure.
In addition, all of the above-mentioned methods require quite a long time to recover a sufficient amount of oils and fats, and therefore, efficient extraction cannot be performed.
Further, since cells are destructed in an organic solvent, which entails the risk of fire, the method raises the problem of safety. If fire extinguishing equipment is to be installed to overcome such disadvantages, enormous cost is required, making the method uneconomical.
In order to solve these problems, there has been proposed a method in which cells dispersed in water are subjected to mechanical destruction and then brought to dryness, followed by introduction into a column, to thereby extract oils and fats by use of a solvent (Japanese Patent Application Laid-Open (kokai) No. 5-17796).
According to this method, the extraction ratio is high, and liposoluble components contained in microbial cells can be extracted and recovered in a safe manner. However, it has a drawback; finely divided fine powder particles clog the extraction column, thereby requiring prolonged time for extraction.